The invention relates to the voltage supply of certain systems by other systems, via a power cable.
As is known to those skilled in the art, certain systems such as certain vehicles, such as cars, must be recharged by other systems, such as for instance a recharge point (recharge terminal or outlet), in order to be able to continue operating, at least partially.
For instance, in a non-limiting case of a hybrid or fully electric vehicle, the electrical connection of the vehicle to a recharge point is aimed at permitting the recharging of its (their) rechargeable electric battery or batteries.
In particular, but not exclusively, the invention is aimed at the alternating power supply.
In certain countries or regions, standards govern the power supply of certain systems.
This is the case for the ISO/IEC 61851-1 standard that relates to the recharging of electric batteries for vehicles. This standard defines four “charge modes”, one for DC voltage and three for AC voltage (mode 1: direct charge using a simple outlet, for instance, domestic; mode 2: charge using a simple outlet, for instance domestic, through a box that is part of the interconnecting power cable; mode 3: charge using a public or private recharge terminal, more complex than a simple outlet).
For mode 3, the recharge terminal provides a high current voltage if and only if an adequate communication is established on a so-called “pilot” line that is part of the interconnecting power cable and comprising a pilot wire and a ground wire, forming together a part of a simple communication network between the recharge terminal and the vehicle. The communication can also permit the recharge terminal to indicate at the vehicle the maximum current value that the recharge terminal can provide vehicle with.
More specifically, in this mode 3, the recharge terminal generates, going to the vehicle, a rectangular signal (for instance with a frequency equal to 1 kHz), for which the pulse width is representative of the maximum current value that it can provide to the vehicle. This signal is of the PWM (pulse width modulation) type. At the vehicle, the electric link with the pilot line is coupled, on the one hand to an analysis module, and on the other hand, to at least a diode and a first resistance mounted in series (one can also provide for a second resistance and a switch mounted in parallel to the first resistance).
Since the first resistance is coupled to the ground wire and to ground (generally the chassis), it permits, when the vehicle-recharge terminal coupling is in good order (especially with respect to ground), to signal this conformity to the recharge terminal. The analysis module is asked to measure the pulse width of the rectangular signals of the first signal (at all times during the charge) in order to determine the maximum current value offered by the recharge terminal so as never to consume a recharge current exceeding this maximum available value. One will observe that the latter is generally situated between 6 Amp and 80 Amp per phase.
The second resistance and the switch are called upon to signal to the recharge terminal whether or not it is authorized to supply power to the vehicle, according to whether the switch is open or closed. One will notice that in the absence of a second resistance and switch as soon as the vehicle-recharge terminal is established in good order, the recharge terminal can supply current.
One will also observe that a vehicle-recharge communication similar to the one described is implemented in mode 2 above via the interconnecting power cable box.
When the vehicle and the recharge terminal (for instance) must exchange information other than the information related to the maximum current value available, such as, for instance, information related to the billing of the recharge or to the available electric power management, another communication must be established between them. This other communication can take place through two modems on the vehicle and the recharge terminal, respectively, generally via the technique called PLC (“Power Line Communication”). In particular, according to the technologies known to one of ordinary skill in the art, these modems are connected to one of the links of the vehicle and the recharge terminals that are dedicated to the power lines, generally via analog coupling circuits (comprising capacitors and/or electromagnetic cores) so as not to interfere with the power supply and so as not to disturb the first signal that flows through the pilot line. Unfortunately, this type of communication on a power line induces high crosstalk in many instances and consequently, the information exchange can be picked up relatively easily by communication equipment located near the vehicle and the recharge terminal, such as nearby vehicle modems, which harms the confidentiality and the safety of the transactions.